ZED-F9P - Integration manual
The AssistNow Offline service benefits u-blox GNSS receivers that only have occasional internet
access. Users request data from the service by specifying the time period for which they want
coverage (1 to 5 weeks).
The data downloaded from the service is organized by date and encoded into a sequence of UBX
MGA messages.
The ZED-F9P supports AssistNow Online only.
3.9.1 Authorization
The AssistNow Online Service is only available for use by u-blox customers. In order to use the
services, customers will need to obtain an authorization token from u-blox. This token must be
supplied as a parameter whenever a request is made to either service. Please contact your local
technical support or go to https://www.u-blox.com/en/solution/services/assistnow to get more
information and request an authorization token.
3.9.2 Multiple servers
The implementation of the AssistNow Online Service is designed to be highly available and reliable.
Nonetheless, there will be rare occasions when a server is not available (e.g. due to failure or some
form of maintenance activity). In order to protect customers against the impact of such outages,
u-blox runs at least two instances of the AssistNow Online Service on independent machines.
Customers have a choice of requesting assistance data from any of these servers, as all will provide
the same information. However, should one fail for whatever reason, it is highly unlikely that the
other server(s) will also be unavailable. Therefore customers requiring the best possible availability
are recommended to implement a scheme where they direct their requests to a chosen server, but,
if that server fails to respond, have a fallback mechanism to use another server instead.
3.9.3 Preserving information during power-off
The performance of u-blox receivers immediately after they are turned on is enhanced by providing
them with as much useful information as possible. AssistNow services are one way to achieve this,
but retaining information from previous use of the receiver can be just as valuable. All the types of
data delivered by assistance can be retained while the receiver is powered down for use when power
is restored. Obviously the value of this data will diminish as time passes, but in many cases it remains
very useful and can significantly improve time to first fix.
There are several ways in which a u-blox receiver can retain useful data while it is powered down,
including:
•
Battery-backed RAM:
The receiver can be supplied with sufficient power to maintain a small
portion of internal storage, while it is otherwise turned off. This is the best mechanism,
provided that the small amount of electrical power required can be supplied continuously.
V_BCKP is the pin to sustain battery-backed RAM.
•
Save-on-Shutdown:
The receiver can be instructed to dump its current state to flash memory
as part of the shutdown procedure; this data is then automatically retrieved when the receiver
is restarted. For more information, see the description of the UBX-UPD-SOS messages in the
ZED-F9P Interface description [
].
3.9.4 AssistNow Online
AssistNow Online is u-blox's end-to-end Assisted GNSS (A-GNSS) solution for receivers that have
access to the internet. Data supplied by the AssistNow Online Service can be directly uploaded to
a u-blox receiver in order to substantially reduce time to first fix (TTFF), even under poor signal
conditions (typically around 2 seconds; see ZED-F9P Data sheet [
] "Aided start"). The system
UBX-18010802 - R08
3 Receiver functionality
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Early production information
